U.S. patent number 4,983,023 [Application Number 07/254,036] was granted by the patent office on 1991-01-08 for liquid crystal display panel with polymer spacers containing a percentage of epoxy groups.
This patent grant is currently assigned to Kitazawa Yakuhin Co., Ltd., Sharp Kabushiki Kaisha, Tosoh Corporation. Invention is credited to Takashi Kitamura, Takeshi Kitazawa, Kenichi Nakagawa.
United States Patent |
4,983,023 |
Nakagawa , et al. |
January 8, 1991 |
Liquid crystal display panel with polymer spacers containing a
percentage of epoxy groups
Abstract
A liquid crystal display panel comprises at least two base
plates spaced by a sealant on the peripheral portion of the plates
and liquid crystal in the space between the base plates. The liquid
crystal contains a spacer of rigid particles and polymer particles
having 10 to 30% by weight of an epoxy group.
Inventors: |
Nakagawa; Kenichi (Nara,
JP), Kitazawa; Takeshi (Nishinomiya, JP),
Kitamura; Takashi (Yamaguchi, JP) |
Assignee: |
Sharp Kabushiki Kaisha (Osaka,
JP)
Kitazawa Yakuhin Co., Ltd. (Osaka, JP)
Tosoh Corporation (Yamaguchi, JP)
|
Family
ID: |
17276156 |
Appl.
No.: |
07/254,036 |
Filed: |
October 6, 1988 |
Foreign Application Priority Data
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Oct 7, 1987 [JP] |
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62-255252 |
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Current U.S.
Class: |
349/157 |
Current CPC
Class: |
G02F
1/13392 (20130101) |
Current International
Class: |
G02F
1/1339 (20060101); G02F 1/13 (20060101); G02F
001/133 () |
Field of
Search: |
;350/339R,344
;523/414 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0050357 |
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Apr 1982 |
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EP |
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0216632 |
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Apr 1987 |
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EP |
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1083520 |
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Apr 1986 |
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JP |
|
Primary Examiner: Miller; Stanley D.
Assistant Examiner: Gross; Anita Pellman
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch
Claims
What is claimed is:
1. A liquid crystal display panel comprising at least two base
plates spaced by a sealant on the peripheral portion of the plates
and liquid crystal in the space between the base plates, wherein
said liquid crystal contains as a spacer rigid particles and
polymer particles having 10 to 30% by weight of an epoxy group.
2. The liquid crystal display panel according to claim 1 wherein
said rigid particles are one of glass fiber, plastic particles and
inorganic particles.
3. The liquid crystal display panel according to claim 1 wherein
said polymer particles are acrylic polymer particles which are
treated with polyglycidyl ether.
4. The liquid crystal display panel according to claim 1 wherein
said polymer particles are prepared by polymerizing an epoxy
group-containing vinyl monomer.
5. The liquid crystal display panel according to claim 1 wherein
said base plates have a film formed thereon and wherein said epoxy
groups of the polymer particles react with the film and base plates
to chemically bond thereto.
6. The liquid crystal display panel according to claim 1 wherein
said polymer particles are selected from the group consisting of
acrylic crosslinked particles, styrene crosslinked particles, ester
crosslinked particles, and urethane crosslinked particles.
7. The liquid crystal display panel according to claim 1 wherein
the epoxy group is introduced by treating the polymer particles
with epihalohydrine or polyglycidyl ether.
8. The liquid crystal display panel according to claim 1 wherein
the polymer particles contain 20 to 30% by weight of an epoxy
group.
9. The liquid crystal display panel according to claim 1 wherein
the polymer particles contain 28 to 29% by weight of an epoxy
group.
Description
FIELD OF THE INVENTION
The present invention relates to a liquid crystal display
panel.
BACKGROUND OF THE INVENTION
A liquid crystal display panel is generally composed of two base
plates spaced at a constant distance and liquid crystal sealed in
the space between the base plates. The distance of the space is
generally referred to as "cell thickness".
In order to obtain a high quality liquid crystal display panel, a
uniform cell thickness is primarily required. The uniform cell
thickness is usually realized by the following methods:
(1) The base plate is changed to a hard and thick one having a
thickness of 3 to 5 mm.
(2) An inside pressure of the liquid crystal display panel is lower
than the outside pressure, i.e., atmospheric pressure.
In the method (1), the display panel is heavy, and a displayed
image and a shadow thereof result in a double image. In the method
(2), if the volume of the liquid crystal is reduced at a low
temperature, the inside pressure is further lower and finally it
develops bubbles having an almost vaccuum pressure, i.e.,
"low-temperature bubble" phenomenon.
It is also proposed that a spacer, such as a film, particles, glass
fiber and the like, is held between the base plates. If it is
desired that the cell thickness is highly uniform, the spacer is
used in a quite large amount.
However, if the spacer is used in such a large amount, the cell
thickness is held too strongly for the base plates to bend. Bending
generally absorbs the volume reduction for the liquid crystal at
low temperatures. The amount of bending becomes too small to absorb
it, however when the plates are held strongly.
It is therefore desired that the liquid crystal display panel has a
uniform cell thickness and does not develop low-temperature bubble
phenomenon.
SUMMARY OF THE INVENTION
It has been found that the above problems are obviated by a
combination of the conventional spacer with particular polymer
particles. The present invention provides a liquid crystal display
panel comprising at least two base plates spaced by a sealant on
the peripheral portion of the plates and liquid crystal in the
space between the base plates, wherein said liquid crystal contains
a spacer of rigid particles and polymer particles having 10 to 30%
by weight of an epoxy group.
Further scope of applicability of the present invention will become
apparent from the detailed description given hereinafter. However,
it should be understood that the detailed description and specific
examples, while indicating preferred embodiments of the invention,
are given by way of illustration only, since various changes and
modifications within the spirit and scope of the invention will
become apparent to those skilled in the art from this detailed
description.
BRIEF EXPLANATION OF THE DRAWINGS
The present invention will become more fully understood from the
detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus, are
not limitative of the present invention, and wherein:
FIG. 1 schematically shows a sectional view of liquid crystal
display plates of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Two base plates 1 are spaced at a distance d, in which a liquid
crystal 2 is held and sealed. The plates 1 are adhered with an
adhesive agent 3. Although not shown in FIG. 1, transparent
conductive film, color filters, thin film transistors and/or
nonlinear elements are formed on the bases plates 1, if necessary.
The base plate can be obtained from glass, plastics, and the like.
The base plate 1 is subjected to an orientation treatment. The cell
thickness d is generally 1 to 20 microns. The liquid crystal can be
a nematic liquid crystal, a smectic A liquid crystal or a
ferroelectric smectic liquid crystal.
According to the present invention, the rigid particles 4 and the
polymer particles 5 are used as spacer. The rigid particles 4 are
those known as a spacer, such as glass fibers, plastic particles,
inorganic particles and the like. The polymer particles 5 include
acrylic crosslinked particles, styrene crosslinked particles, ester
crosslinked particles, urethane crosslinked particles and the like.
According to the present invention, it is characterized that the
polymer particles 5 contains 10 to 30% by weight, preferably 20 to
30% by weight, and more preferably 28 to 29% by weight of an
unreacted epoxy group based on the total resin amount. The epoxy
group may be introduced by treating the polymer particles with
epihalohydrine or polyglycidyl ether, such as triglycidyl ether and
the like. An epoxy-group-containing vinylmonomer, such as glycidyl
(meth)acrylate, may be polymerized to form the polymer particles 5
having an epoxy group. It is believed that the epoxy groups of the
polymer particles 5 reacts with an OH group, an NH group or an SH
group of the orientation film or the base plate.
In order to obtain the display panel of the present invention, the
rigid particles and the polymer particles are adhered onto one of
the base plate. This can be done by placing the base panel in the
chamber containing both particles. The base plate 1 may be treated
with a liquid containing the particles and then dried. The adhesive
agent 3 is then applied to the peripheral portion of the base plate
to which the other base plate is pressed at an elevated
temperature. The rigid particles 4 secure the minimum value of the
cell thickness. The polymer particles 5 are transformed and adhered
to the base plates 1 by the function of heat and pressure. The
resultant empty panel is then cooled to room temperature, at which
the transformed polymer particles 5 retain their forms. A liquid
crystal 2 is introduced into the space formed between the plates
and the plates are then sealed at the inlet to obtain a liquid
crystal display panel of the present invention.
It is preferred that the polymer particles 5 of the present
invention has a low elastic modulas.
EXAMPLES
The present invention is illustrated by the following Examples
which, however, are not to be construed as limiting the scope of
the present invention to their details.
EXAMPLE 1
Glass fiber having an average diameter of 7.5 microns and a
standard deviation of diameter of 0.15 microns was cut to a length
of 10 to 20 microns. One part by weight of the glass fiber and 5
parts by weight of polymer particles available from Tosoh
Corporation. as Toyo Spacer (average diameter=9.0 microns, standard
deviation of diameter=1 micron, epoxy content=29%) were mixed and
20 mg of the mixture was put in a clean chamber of 100 liter to
form aerosol. A glass plate having a thickness of 1 mm was put in
the aerosol for 5 seconds to adhere the spacer mixture on the
panel. Another glass plate was screen-printed with an epoxy
adhesive agent to form a seal pattern and contacted with the
spacered glass plate. It was heated to 120.degree. C. for 2 hours
under pressure of 1 Kg/cm.sup.2 to cure the adhesive agent and
simultaneously contact the polymer particles with the glass plate.
The obtained panel not containing liquid crystal has a thickness of
7.58.+-.0.06 microns. Nematic liquid crystal was introduced into
the cell by a vacuum method and sealed with a ultraviolet-curing
adhesive agent to obtain a liquid crystal panel. The panel was
allowed to stand at -30.degree. C. for one hour, but no low
temperature bubbles were seen.
EXAMPLE 2
One part by weight of plastic powder having an average diameter of
7 microns and a standard deviation of diameter of 0.3 microns and 5
parts by weight of polymer particles available as Toyo Spacer
(average diameter=9.0 microns, standard deviation of diameter=1
micron, epoxy content=29%) were mixed and 20 mg of the mixture was
put in a clean chamber of 100 liter to form aerosol. A glass plate
having a thickness of 1 mm was put in the aerosol for 5 seconds to
place the spacer mixture on the panel. Another glass plate was
screen-printed with an epoxy adhesive agent to form a seal pattern
and contacted with the spacered glass plate. It was heated to
120.degree. C. for 2 hours under pressure 1 Kg/cm.sup.2 to cure the
adhesive agent and simultaneously contact the polymer particles
with the glass plate. The obtained panel not containing liquid
crystal has a thickness of 7.32.+-.0.08 microns. Nematic liquid
crystal was introduced into the cell by a vacuum method and sealed
with a ultraviolet-curing adhesive agent to obtain a liquid crystal
plate. The plate was allowed to stand at -30.degree. C. for one
hour, but no low temperature bubbles were seen.
EXAMPLE 3
One part by weight of silicon dioxide particles having an average
diameter of 2.2 microns and a standard deviation of diameter of
0.15 microns and 5 parts by weight of polymer particles available
from Tosoh Corporation as Toyo Spacer (average diameter=3.5
microns, standard deviation of diameter=0.2 micron, epoxy
content=29 %) were mixed and 20 mg of the mixture was put in a
clean chamber of 100 liter to form aerosol. A glass plate having a
thickness of 1 mm was put in the aerosol for 5 seconds to place the
spacer mixture on the plate. Another glass plate was screen-printed
with an epoxy adhesive agent to form a seal pattern and contacted
with the spacered glass plate. It was heated to 120.degree. C. for
2 hours under pressure of 1 Kg/cm.sup.2 to cure the adhesive agent
and simultaneously contact the polymer particles with the glass
plate. The obtained panel not containing liquid crystal has a
thickness of 2.28.+-.0.02 microns. Ferroelectric smectic liquid
crystal was poured into the panel by a vacuum method and sealed
with a ultraviolet-curing adhesive agent to obtain a liquid crystal
panel. The panel was allowed to stand at -30.degree. C. for one
hour, but no low temperature bubbles were seen.
The invention being thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *